import torch
from collections import OrderedDict
from os import path as osp
from tqdm import tqdm

from basicsr.archs import build_network
from basicsr.losses import build_loss
from basicsr.metrics import calculate_metric
from basicsr.utils import get_root_logger, imwrite, tensor2img
from basicsr.utils.registry import MODEL_REGISTRY
from .base_model import BaseModel


@MODEL_REGISTRY.register()
class SRModel(BaseModel):
    """Base SR model for single image super-resolution."""

    def __init__(self, opt):
        super(SRModel, self).__init__(opt)

        # define network
        self.net_g = build_network(opt["network_g"])
        self.net_g = self.model_to_device(self.net_g)
        self.print_network(self.net_g)

        # load pretrained models
        load_path = self.opt["path"].get("pretrain_network_g", None)
        if load_path is not None:
            param_key = self.opt["path"].get("param_key_g", "params")
            self.load_network(self.net_g, load_path, self.opt["path"].get("strict_load_g", True), param_key)

        if self.is_train:
            self.init_training_settings()

    def init_training_settings(self):
        self.net_g.train()
        train_opt = self.opt["train"]

        self.ema_decay = train_opt.get("ema_decay", 0)
        if self.ema_decay > 0:
            logger = get_root_logger()
            logger.info(f"Use Exponential Moving Average with decay: {self.ema_decay}")
            # define network net_g with Exponential Moving Average (EMA)
            # net_g_ema is used only for testing on one GPU and saving
            # There is no need to wrap with DistributedDataParallel
            self.net_g_ema = build_network(self.opt["network_g"]).to(self.device)
            # load pretrained model
            load_path = self.opt["path"].get("pretrain_network_g", None)
            if load_path is not None:
                self.load_network(self.net_g_ema, load_path, self.opt["path"].get("strict_load_g", True), "params_ema")
            else:
                self.model_ema(0)  # copy net_g weight
            self.net_g_ema.eval()

        # define losses
        if train_opt.get("pixel_opt"):
            self.cri_pix = build_loss(train_opt["pixel_opt"]).to(self.device)
        else:
            self.cri_pix = None

        if train_opt.get("perceptual_opt"):
            self.cri_perceptual = build_loss(train_opt["perceptual_opt"]).to(self.device)
        else:
            self.cri_perceptual = None

        if self.cri_pix is None and self.cri_perceptual is None:
            raise ValueError("Both pixel and perceptual losses are None.")

        # set up optimizers and schedulers
        self.setup_optimizers()
        self.setup_schedulers()

    def setup_optimizers(self):
        train_opt = self.opt["train"]
        optim_params = []
        for k, v in self.net_g.named_parameters():
            if v.requires_grad:
                optim_params.append(v)
            else:
                logger = get_root_logger()
                logger.warning(f"Params {k} will not be optimized.")

        optim_type = train_opt["optim_g"].pop("type")
        self.optimizer_g = self.get_optimizer(optim_type, optim_params, **train_opt["optim_g"])
        self.optimizers.append(self.optimizer_g)

    def feed_data(self, data):
        self.lq = data["lq"].to(self.device)
        if "gt" in data:
            self.gt = data["gt"].to(self.device)

    def optimize_parameters(self, current_iter):
        self.optimizer_g.zero_grad()
        self.output = self.net_g(self.lq)

        l_total = 0
        loss_dict = OrderedDict()
        # pixel loss
        if self.cri_pix:
            l_pix = self.cri_pix(self.output, self.gt)
            l_total += l_pix
            loss_dict["l_pix"] = l_pix
        # perceptual loss
        if self.cri_perceptual:
            l_percep, l_style = self.cri_perceptual(self.output, self.gt)
            if l_percep is not None:
                l_total += l_percep
                loss_dict["l_percep"] = l_percep
            if l_style is not None:
                l_total += l_style
                loss_dict["l_style"] = l_style

        l_total.backward()
        self.optimizer_g.step()

        self.log_dict = self.reduce_loss_dict(loss_dict)

        if self.ema_decay > 0:
            self.model_ema(decay=self.ema_decay)

    def test(self):
        if hasattr(self, "net_g_ema"):
            self.net_g_ema.eval()
            with torch.no_grad():
                self.output = self.net_g_ema(self.lq)
        else:
            self.net_g.eval()
            with torch.no_grad():
                self.output = self.net_g(self.lq)
            self.net_g.train()

    def dist_validation(self, dataloader, current_iter, tb_logger, save_img):
        if self.opt["rank"] == 0:
            self.nondist_validation(dataloader, current_iter, tb_logger, save_img)

    def nondist_validation(self, dataloader, current_iter, tb_logger, save_img):
        dataset_name = dataloader.dataset.opt["name"]
        with_metrics = self.opt["val"].get("metrics") is not None
        use_pbar = self.opt["val"].get("pbar", False)

        if with_metrics:
            if not hasattr(self, "metric_results"):  # only execute in the first run
                self.metric_results = {metric: 0 for metric in self.opt["val"]["metrics"].keys()}
            # initialize the best metric results for each dataset_name (supporting multiple validation datasets)
            self._initialize_best_metric_results(dataset_name)
        # zero self.metric_results
        if with_metrics:
            self.metric_results = {metric: 0 for metric in self.metric_results}

        metric_data = dict()
        if use_pbar:
            pbar = tqdm(total=len(dataloader), unit="image")

        for idx, val_data in enumerate(dataloader):
            img_name = osp.splitext(osp.basename(val_data["lq_path"][0]))[0]
            self.feed_data(val_data)
            self.test()

            visuals = self.get_current_visuals()
            sr_img = tensor2img([visuals["result"]])
            metric_data["img"] = sr_img
            if "gt" in visuals:
                gt_img = tensor2img([visuals["gt"]])
                metric_data["img2"] = gt_img
                del self.gt

            # tentative for out of GPU memory
            del self.lq
            del self.output
            torch.cuda.empty_cache()

            if save_img:
                if self.opt["is_train"]:
                    save_img_path = osp.join(self.opt["path"]["visualization"], img_name, f"{img_name}_{current_iter}.png")
                else:
                    if self.opt["val"]["suffix"]:
                        save_img_path = osp.join(self.opt["path"]["visualization"], dataset_name, f'{img_name}_{self.opt["val"]["suffix"]}.png')
                    else:
                        save_img_path = osp.join(self.opt["path"]["visualization"], dataset_name, f'{img_name}_{self.opt["name"]}.png')
                imwrite(sr_img, save_img_path)

            if with_metrics:
                # calculate metrics
                for name, opt_ in self.opt["val"]["metrics"].items():
                    self.metric_results[name] += calculate_metric(metric_data, opt_)
            if use_pbar:
                pbar.update(1)
                pbar.set_description(f"Test {img_name}")
        if use_pbar:
            pbar.close()

        if with_metrics:
            for metric in self.metric_results.keys():
                self.metric_results[metric] /= idx + 1
                # update the best metric result
                self._update_best_metric_result(dataset_name, metric, self.metric_results[metric], current_iter)

            self._log_validation_metric_values(current_iter, dataset_name, tb_logger)

    def _log_validation_metric_values(self, current_iter, dataset_name, tb_logger):
        log_str = f"Validation {dataset_name}\n"
        for metric, value in self.metric_results.items():
            log_str += f"\t # {metric}: {value:.4f}"
            if hasattr(self, "best_metric_results"):
                log_str += (
                    f'\tBest: {self.best_metric_results[dataset_name][metric]["val"]:.4f} @ ' f'{self.best_metric_results[dataset_name][metric]["iter"]} iter'
                )
            log_str += "\n"

        logger = get_root_logger()
        logger.info(log_str)
        if tb_logger:
            for metric, value in self.metric_results.items():
                tb_logger.add_scalar(f"metrics/{dataset_name}/{metric}", value, current_iter)

    def get_current_visuals(self):
        out_dict = OrderedDict()
        out_dict["lq"] = self.lq.detach().cpu()
        out_dict["result"] = self.output.detach().cpu()
        if hasattr(self, "gt"):
            out_dict["gt"] = self.gt.detach().cpu()
        return out_dict

    def save(self, epoch, current_iter):
        if hasattr(self, "net_g_ema"):
            self.save_network([self.net_g, self.net_g_ema], "net_g", current_iter, param_key=["params", "params_ema"])
        else:
            self.save_network(self.net_g, "net_g", current_iter)
        self.save_training_state(epoch, current_iter)
